The Affordable Care Act adds or amends more than 40 provisions of the U.S. tax code.

A bunch are intended strictly to raise revenue -- for instance, a new tax on medical device makers. But others are designed to encourage certain behaviors, such as the mandate that individuals buy insurance or pay a penalty.

It's hard to keep track of all the new parts. Some took effect in 2010, when the law was enacted. Others began in 2011, 2012 or this year. Several will hit next year and at least one provision won't kick in until 2018. One, meanwhile, has been delayed a year. The employer mandate, which requires employers with 50 or more full-time workers to provide qualified, affordable health insurance, will now go into effect in 2015.

What's more, even though many of the Obamacare tax changes are permanent, some are temporary, and in a few cases have already expired.

Meanwhile, the rules governing some of them can be complex. High-income taxpayers, for instance, may come to really appreciate their accountants when it comes to figuring out whether a new Medicare tax applies to a portion of their capital gains and dividends.

To help sort through it all, here's a guide to some of the key tax provisions in the health reform law for: